The organization of perseverative means -end coordination in infancy

Abstract

Infants begin to coordinate their actions into means-end sequences at eight to nine months of age, as indicated by their willingness to search for objects that are occluded, and by their ability to use supports to pull distant objects within reach. However, the occurrence of perseverative responses like the A-not-B error through the end of the first year suggests an inflexibility in means-end actions, in that infants fail to respond on the basis of context-specific information, but rather respond on the basis of previously rewarded action. The purpose of the current study was to evaluate two antithetical explanations of infant search errors--one that attributes errors solely to repeated motor experience, and one that invokes the notion of representational, or working memory to describe means-end search.^ Nine-, twelve-, and eighteen-month-old infants were tested on a violation of expectation search procedure. Infants were given repeated practice pulling down a screen to retrieve a toy. After several trials, a second identical screen was surreptitiously inserted behind the first, forcing infants to adapt their search behavior to the novel layout in order to successfully retrieve the toy. Infants at the three ages were tested on an 'opaque' condition, in which both of the screens were opaque and covered with an identical checkerboard pattern. Nine- and twelve-month-olds were also tested in two control conditions. In the 'transparent' control condition, the two screens were fitted with plexiglass windows, thus eliminating the need to represent the existence of the toy. In the 'no-toy' control condition, the screens were opaque, but no toys were hidden and subjects were simply given a series of trials with one screen and then tested with two screens.^ The results supported the working memory, representational account of infant search. In the opaque condition, most nine-month-olds searched for the toy behind the second cover. Twelve-month-olds, however, were less likely than the nine-month-olds to pull down both screens, and frequently persisted in their efforts to find the toy behind the first screen. Infants in the two control conditions did not have this difficulty extending their action to the second screen. Eighteen-month-olds quickly solved the double-cover problem, rapidly pulling down both screens. The poorer performance of the twelve-month-olds suggests that they accurately represented the location of the toy where they had seen it hidden (behind the first screen), and thus failed to consider the second screen as a possible hiding location for the toy. ^